The present invention relates to scrambling and descrambling of cable television signals. A number of different scrambling methods have been employed in the past to prevent unauthorized reception of premium cable television programs for which a charge is usually imposed. Some systems incorporate subscriber addressing in which data is transmitted from a head-end scrambler to individual subscriber units. Upon proper address identification, descrambling circuitry is activated to enable reception of the authorized programming. However, many of the systems in use today are either too easily defeated or use overly complex scrambling techniques some of which introduce spurious and undesirable signals into the television signal. A need exists for a system which offers simplicity of design and yet increased security over existing systems.